The box office is where tickets are sold. It is also the commercial revenue generated by a film's ticket sales. When a film grosses $100 million at the box office, it has sold that much in tickets. The term comes from the literal box office in a theater, where patrons bought tickets. The number is reported weekly, sometimes daily, and it drives headlines, careers, and studio decisions.

Box office numbers are more complicated than they look. The gross is not the same as the studio's revenue. Theaters keep a share of ticket sales, often 40 to 50 percent, though the split varies by film and by week. A film that grosses $500 million worldwide may return only $250 million to the studio. Marketing costs can add another $100 million or more. A film can be a box office hit and still lose money.

Box office performance is measured in several ways. Domestic gross is the revenue from the United States and Canada. International gross is from other countries. Worldwide gross is the sum. Opening weekend is the first three or four days of release. It is a key indicator of a film's commercial trajectory. A strong opening suggests word of mouth will carry the film. A weak opening can doom a film before it finds an audience.

Box office data is tracked by studios, distributors, and analysts. It is published by outlets like Box Office Mojo. It is a scorecard for the industry, and it shapes which films get made.